Torque tubes are typically used for transmitting power, e.g., from a drive unit to a driven unit. For example, a vehicle, such as an automobile, may utilize a torque tube for transferring power, e.g., from a transmission to a differential. In this application, a torque tube may be referred to as a propeller shaft or a drive shaft. In another example, a torque tube may be used in an aircraft control system for transmitting torsional forces to control surfaces, such as ailerons and flaps.
A typical torque tube is hollow and has an elongated shape. The torque tube may be made of aluminum or from other suitable materials capable of withstanding the torque transferred through the tube. During the manufacturing process, end fittings with outer surfaces having angular ridges are inserted into the ends of the torque tube. The ends of the tube are then conformed to (swaged over) the end fittings to form complementary geometric features on the inner surface of the tube for torque tube engaging the angular ridges of the end fittings. The above-described couplings prevent slippage of the end fittings with respect to the torque tube and transfer torsional loads between the end fittings and the tube section.
When a torque tube is conformed to end fittings configured as described above, the walls of the tube may become susceptible to cracking. These cracks may reduce the expected life of the tube and parts containing cracks should be removed from service.